For this is the will of my father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day.”
John 6:40
This is the will of God, that we should look upon the Son and believe in Him, resulting in eternal life. Eternal life is not only the quantity of life but the quality of life, beginning with beholding and believing. Jesus came so that we would have a quality of life filled with every spiritual blessing found in the heavenlies. It is as we see Jesus that we enter into this quality of life, John 14:19, and are enabled to freely give what we have freely received.
As Jesus was the expression of His Father, we become as He is in this process of beholding. Jesus proclaimed, ‘I and the Father are one.’ ‘He who has seen me has seen the Father.’ Whoever sees me, sees Him who sent me.’ Jesus’ purpose was to manifest the Father. Our purpose now is to manifest Jesus.
Ellicott's Commentary for English Readers states the following on this passage -
“And this is the will of him that sent me.—Read, For this is the will of My Father. (See John 6:39.) The common text has inserted the opening words of these verses. There can be no doubt that the change indicated gives the original reading, and it will be seen that the relation of “Father” and “Son” is thus preserved.
Every one which seeth the Son.—We pass here to the individuals who compose the great mass of humanity. It is the divine will that no one should be excluded, but that he may have eternal life (comp. John 3:15; John 5:24): this is the Father’s gift in the person of the Son. The exercise of the mental power to see Him, the reception of Him and trust upon Him: this is man’s acceptance of God’s gift. The word rendered “seeth” means to look upon, to contemplate, and is the first step towards a true faith.”
From Helps Word Studies the Greek word seeth is defined ~
“2334 theōréō (from 2300 /theáomai, "to gaze, contemplate") – gaze on for the purpose of analyzing(discriminating).
2334 (theōréō) is the root of the English term "theatre," i.e., where people concentrate on the meaning of an action (performance).”
To ‘see’ Jesus there must be a ‘contemplative gazing’ of scripture, a meditation of the words until there is wisdom and understanding. Much like Joshua 1:8, ‘This book of the law shall not depart out of your mouth, but you shall meditate on it day and night, so that you may be careful to do all according to all that is written in it. THEN you shall make your way prosperous and THEN you shall have good success.
It is the transformation process of renewing our minds that enables us to ‘see’ Him as He is and become like Him. We saw that transformation comes from beholding, and we understand that transformation is always done by the power of the Holy Spirit as we yield to His workings. The Holy Spirit works within us, bringing us into the revelation (wisdom and understanding) of the Father and of His Son.
This knowledge is eternal life, John 17:3, and eternal life begins for the one who looks upon Jesus and believes in Him.